1. Field of the Invention
This invention relates to a part life detection and display unit for detecting and displaying the lives of a large number of periodically replaced parts used in image formation systems such as color copiers and color printers.
2. Description of the Related Art
A large number of periodically replaced parts such as photosensitive drums, corotron wires, and developers are used in color copiers, etc. To detect and display the lives of such periodically replaced parts, for example, a detection and display system is employed wherein the use results of the periodically replaced parts are measured based on indexes such as the number of copies, the part operation time, and the number of times the part has been operated for each part and when the measured cumulative value reaches a replacement alarm value preset based on the indexes, the part is assumed to reach "part life" and a replacement message for prompting the operator to replace the part is displayed.
However, since such a part life detection and display system manages the life of each periodically replaced part by measuring each index, the arrival time until the measured cumulative value reaches the replacement alarm value also varies from one part to another. Resultantly, parts reach their respective replacement alarm values one after another at one time and must be replaced each time in a short time. Such a circumstance tends to occur more remarkably in color copiers.
Thus, replacement work of servicepersons, etc., becomes intricate and the work efficiency extremely worsens because of repeated part replacement in a short time. Moreover, if a large number of parts different in attachment place must be replaced at a time, management of the parts to be replaced and work are placed out of order, replacement of some parts is forgotten because of some mistake, and use of the unreplaced parts in a state in which their replacement alarm values are exceeded will lead to a failure.
A system similar to the detection and display system is a system wherein the use results and replacement alarm values of periodically replaced parts are all measured and set in terms of the same index and when the measured cumulative value reaches the replacement alarm value in terms of the index, a replacement message is displayed. For example, a part life detection and display unit with the number of copies applied as the index for the purpose is disclosed in Japanese Patent Examined Publication No. Sho 62-36217.
However, the part life detection and display system using term values based on such a common index provides a simple configuration because the number of index measurement objects for managing the part lives is small. In contrast, it involves the following problem:
The arrival time of each periodically replaced part by the time the term value reaches a replacement alarm value often varies widely from one part to another depending on the use mode of a copier, etc., such as the use ratio between color and monochrome copies or the number of continuous copies from a 1-sheet original document). Thus, the arrival time by the time the cumulative value measuring the index for conversion reaches a replacement alarm value also varies widely from one part to another. Resultantly, problems of bad work efficiency of part replacement, forgetting to replace parts, etc., as described above still arise.